Drive Wheel Slip Ratio Control Below the Friction Peak
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Solution Overview
Problem
When traction control is implemented in the area including the µ peak, a wheel exceeding the µ peak can experience an increased slip ratio, leading to a difference in driving force between wheels and the generation of unintended yaw moments.
Innovation Solution
A driving force control device that sets a predetermined slip ratio to an area smaller than the slip ratio corresponding to the peak value of the road surface friction coefficient, and controls the slip ratio within this area by reducing the driving torque when the calculated slip ratio reaches the predetermined value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traction control is implemented in the area including the µ peak, then the driving force is improved, but the vehicle stability deteriorates due to unintended yaw moment generation
Solution Approach 1:
The control device applies preliminary anti-action by detecting when a drive wheel exceeds the µ peak and proactively reducing the driving torque to counteract the developing yaw moment. The yaw moment counteracting control reduces the driving torque of the drive source when the slip ratio exceeds the µ peak, preventing the vehicle from deviating from the intended trajectory and maintaining stability while preserving adequate driving force.
2Power
If the slip ratio is increased to reach the µ peak, then the traction performance is improved, but the difference in driving force between wheels increases causing yaw moment
Solution Approach 1:
The control device employs feedback by continuously monitoring the slip ratio of each drive wheel and comparing it against the µ peak threshold. When the slip ratio exceeds the µ peak, the system feedback-reduces the driving torque to eliminate the driving force difference between wheels, preventing unintended yaw moments and maintaining predictable vehicle behavior while preserving adequate traction performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach stabilizes vehicle behavior by preventing excessive slip ratios and minimizing differences in driving force between wheels, thus avoiding unintended yaw moments.
Implementation Method 1
an electric motor 1 that is connected to drive wheels FL and FR via a speed reduction mechanism 3a and a drive shaft 4, and is configured to generate a torque for braking or driving the drive wheels
Implementation Method 2
a friction coefficient μ between a tire and a road surface
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
Provided is a driving force control device capable of stabilizing a vehicle behavior when a driving torque of a drive wheel is controlled. When slip suppression control is carried out to decrease a driving torque of a drive source that is connected to the drive wheel of a vehicle via a speed reduction mechanism and a drive shaft, and is configured to generate a torque for braking or driving the drive wheel, to thereby suppress a slip state of the drive wheel, the driving torque of the drive source is controlled so that a slip ratio of the drive wheel is in an area of the slip ratio smaller than a slip ratio corresponding to a peak value of a road surface friction coefficient in a characteristic of the road surface friction coefficient with respect to the slip ratio.